Conventionally, an artificial heart pump which pumps the blood by utilizing the rotation of the impeller is employed as an alternate being used for medical purposes or as an assist pump being used for medical purposes. An artificial heart pump utilizing a roller pump or a centrifugal pump and an artificial heart pump utilizing an axial-flow pump are provided as the aforementioned artificial heart pump. Among these various types of artificial heart pumps, the artificial heart pump utilizing an axial-flow pump can reduce the size thereof, being compared with the artificial heart pump utilizing a roller pump or a centrifugal pump.
The conventional artificial heart pump utilizing an axial-flow pump includes a housing that houses motor stators therein, and at the same time, includes a rotor being equipped with impellors on the circumference thereof that houses permanent magnets reacting to the motor stators magnetically therein. As an artificial heart pump that has been described hereinabove, as shown in FIG. 24, a following artificial heart pump is provided: wherein, a rotor 104 being equipped with impeller vanes 105 on the outer circumference thereof is installed between fixed bodies 102 and 103 that are fixed to a housing 101; and pivot bearings 106a and 106b are installed to the surfaces where the fixed bodies 102 and 103 face toward the rotor 104. To be specific, by having the centers of the surfaces of the rotor 104 facing the fixed bodies 102 and 103 stick out, the pivot bearings 106a and 106b are formed.
However, when the rotor is supported by the pivot bearings 106a and 106b as shown in FIG. 24, abrasion powders are sometimes generated in the pivot bearings 106a and 106b. In addition, because the gap between the fixed body 102 and the rotor 104 and the gap between the fixed body 103 and the rotor 104 become narrow, there is a possibility that a blood clot may be formed easily or that red blood cells may be destructed.
On the other hand, as shown in FIG. 25, a following artificial heart pump is provided: wherein, the fixed bodies 102 and 103 are connected by the fixed shaft 121; and a rotor 122 having a cylindrical shape, and rotating along the outer circumference of the fixed shaft 121 is installed; and at the same time, hydrodynamic bearings are constructed by providing a groove to each of the surfaces where the rotor 122 faces the fixed bodies 102 ad 103, respectively. To be specific, by having the rotor 122 rotate, hydrodynamic pressures are generated in the grooves that are provided to the surfaces of the fixed bodies 102 and 103 facing the rotor 122, respectively, and thereby, the rotor 122 is prevented from contacting the fixed bodies 102 and 103, and the dynamic bearings behave as thrust bearings. However, when such hydrodynamic bearings are configured as mentioned above, narrow gaps will be necessary for generating the hydrodynamic pressures, and as a result, due to the narrow gaps, there is a possibility that a blood clot may be formed easily or that red blood cells may possibly be destructed.
In order to prevent the above-mentioned problems, the present applicant proposes an artificial heart pump that prevents the rotor from contacting the fixed bodies by passive type of repulsive magnetic bearings, which not only construct the hydrodynamic bearings but also utilize the magnetic forces of repulsion balancing the hydro thrust loads being applied on the impeller vanes. (See the Patent Reference No. 1.) As shown in FIG. 26, in addition to the configuration shown in FIG. 25, the artificial heart pump that is equipped with the passive type of repulsive magnetic bearings has permanent magnets 131 and 132 installed to each of the rotor 122 and the fixed body 103, whereby the passive type of repulsive magnetic bearings are constructed by the magnetic forces of repulsion that balance the hydro thrust loads.    Patent Reference 1: Japanese Patent Application, First Publication No. 2004-346930